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Tuesday, October 23, 2007

Near-Earth

Near-Earth Space Bubbles Mapped

Enormous bubbles of plasma trapped within Earth's magnetic fields have been fully mapped for the first time.

Scientists now think the bubbles of ionized gas, called convection cells, are strongly affected by pummeling from the sun's solar wind. Future observations of the cells could be used to monitor violent solar outbursts, such as solar flares and coronal mass ejections, which can harm satellites or astronauts in space.

"The results are a great achievement," said Philippe Escoubet, the European Space Agency (ESA) project scientist for the experiments aboard the Cluster spacecraft.

Escoubet and his team used six years of data gathered by the two satellite missions to create the maps. "They show data collected over years is helping deepen our understanding of the Sun-Earth connection," Escoubet said.

Convection cells exist high above Earth's polar caps and are made of plasma, which is electron-stripped gas that is highly erratic. Earth's magnetosphere and atmosphere shelter the planet from high-energy solar particles, but the protective shells form an incomplete cocoon-so some of the radiation leaks in, is trapped and forms convection cells.

Scientists think understanding how such particles are trapped is crucial to safeguarding astronauts and satellites, such as GPS and telecommunications platforms.

Prior to the Cluster and Double Star satellites, only poor observations of convection cells could be made. The new statistical maps show that numbers of convection cells fluctuate between two and four, and that their shapes change as solar wind output fluctuates.

Stein Haaland, a scientist at the Max Planck Institute in Germany, said the maps will inform future monitoring of convection cells. "It will be possible to map the region at any altitude, under any conditions with satellites, making our task easier," he said.